(1) Field of the Invention
The present invention relates to a refrigeration cycle, and more particularly to a refrigeration cycle using an ejector in which the refrigeration cycle is applied to an automotive air conditioner.
(2) Description of the Related Art
Conventionally, an ejector cycle formed by using an ejector is known in the field of refrigeration cycles for use in refrigerating apparatuses, such as water heaters, refrigerator vehicles, and automotive air conditioners. The ejector cycle is constructed such that a compressor, a condenser, an ejector, and a gas-liquid separator are connected in series, and a gas outlet of the gas-liquid separator is connected to a suction port of the compressor, while a liquid outlet of the gas-liquid separator is connected to a suction port of the ejector via an evaporator.
The ejector comprises a nozzle having an ejection hole formed in a forward end thereof, a hollow cylindrical mixing portion extending from the outer periphery of the nozzle to the downstream side of the ejection hole, and a diffuser formed such that it is expanded as it extends from the mixing portion. The nozzle decompresses or reduces the pressure of high-temperature, high-pressure liquid refrigerant condensed by the condenser to a pressure not higher than an evaporation pressure, ejects the refrigerant from the forward end thereof as a low-pressure jet stream, and draws gaseous refrigerant from the evaporator by a differential pressure generated by the decompression or reduction of the pressure. In the mixing portion, the gaseous refrigerant drawn from the evaporator and the jet stream ejected from the nozzle are mixed with each other, and in the diffuser, the mixed refrigerant is reduced in flow speed due to an increase in area to have its pressure raised. Due to the rise in the pressure of the refrigerant by the ejector, the suction pressure of the compressor is increased, which makes it possible to reduce a power required for the compressor to compress the refrigerant to a predetermined pressure.
A stable flow of refrigerant is required by the ejector cycle during operation thereof, so that in water heaters, refrigerator vehicles, and automotive air conditioners, a compressor for compressing refrigerant is driven by an electric motor (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2002-22295 (Paragraph No. [0021])), or a sub-engine provided separately from an engine for driving an automotive vehicle (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2000-283577 (Paragraph No. [0014])), and the refrigerating power of the ejector cycle is controlled through control of the rotational speed of the electric motor or the sub-engine.
Particularly when the ejector cycle is applied to a refrigeration cycle for an automotive air conditioner, if the engine for driving an automotive vehicle is used as the drive source of the compressor, the rotational speed of the engine is largely dependent on operating conditions of the vehicle, causing fluctuation of the capacity of the compressor, which makes it difficult to control the ejector cycle. Therefore, another drive source, such as an electric motor or a sub-engine, for driving the compressor is required. Further, the ejector cycle has a large number of control valves and complicated piping, which increases the cost of the automotive air conditioner.